LONDON — Chastised for failing to sing the national anthem, and contradicted by several senior colleagues, the new and left-wing leader of Britain’s opposition Labour Party, Jeremy Corbyn, has had the briefest of political honeymoons.

But on Wednesday, Mr. Corbyn successfully changed the tone of one of Britain’s political traditions — the weekly parliamentary joust between the prime minister and the leader of the opposition — and proved that sometimes it pays just to be polite.

Facing one of the first big tests of his leadership, after two days of critical newspaper headlines, Mr. Corbyn put into practice his promise to do things differently, crowd-sourcing this part of his new job, and posing to Prime Minister David Cameron a selection of questions submitted by voters who offered more than 40,000 suggestions.

The result transformed Prime Minister’s Question Time, a weekly half-hour parliamentary ritual that routinely degenerates into point-scoring against a backdrop of shouting lawmakers.

Instead, a chamber crammed with deputies listened to a series of sober, worthy and slightly technical questions, and their equally serious replies.

The election on Saturday of Mr. Corbyn, who spent three decades as a lawmaker on Labour’s fringes, has highlighted the volatility of politics in Europe, where many voters appear disenchanted with mainstream parties.

But Mr. Corbyn’s ascendancy has reawakened divisions among Labour lawmakers over Europe, welfare spending and membership in NATO. And he has been roundly criticized in Britain’s news media over his failure to sing the national anthem at a ceremony on Tuesday for the 75th anniversary of the Battle of Britain, in which the Royal Air Force held off the German Luftwaffe during World War II.

Mr. Corbyn’s disdain for the monarchy is well known, but his failure to join in singing “God Save the Queen” brought criticism from his own ranks.

On Wednesday, Mr. Corbyn told Sky News that he had “stood in respect” for the duration of the anthem, but was equivocal about whether he would, in the future, sing along. “I showed respect for it, and I’ll show respect in the proper way at all future events,” he said. A Labour Party official later said that this meant he would join in at future events.

Though Mr. Corbyn was elected to the party leadership on Saturday with an overwhelming mandate from party members and supporters eligible to vote, his backing among Labour lawmakers in Parliament is thin.

So the stakes were high at noon on Wednesday in the House of Commons. In a lengthy preface to his first question, Mr. Corbyn said that voters had told him that Prime Minister’s Question Time was “too theatrical,” that ordinary people “wanted things done differently” and that they wanted their voices to be heard.

He asked questions about housing, changes to tax credits (which supplement the income of low earners) and mental health — among the most popular topics of the emails he received, aides later said.

At times, Mr. Corbyn’s style seemed to imitate that of a host of a radio call-in show. “This is absolutely shameful,” Mr. Corbyn said at one point.

“I had more than 1,000 questions on tax credits,” Mr. Corbyn said. “Paul, for example, sends this very heartfelt question: ‘Why is the government taking tax credits away from families? We need this money to survive so our children don’t suffer.’ ”

Mr. Cameron said he welcomed the change of tone, which had been expected. If Prime Minister’s Question Time became more of a “genuine exercise in asking questions and answering questions, no one would be more delighted than me,” he said.

Some early reaction was positive. “You have to say Corbyn won,” Jane Merrick, political editor of The Independent on Sunday, wrote on Twitter, adding that he had done so by “framing the entire exchange” and by forcing Mr. Cameron to be consensual.

Others pointed out that, in raising a variety of topics, Mr. Corbyn sacrificed the ability to focus in on one issue, and ask the type of probing follow-up questions that sometimes catch prime ministers off guard.

Either way, Mr. Corbyn still needs to manage the deep divisions over policy that have surfaced. His decision to appoint a fellow left-winger, John McDonnell, to the sensitive economics portfolio has stoked tension, and at times the party has struggled to hold a coherent line.

The deputy leader, Tom Watson, defended British membership of NATO, an alliance that Mr. Corbyn has criticized.

The shadow foreign secretary, Hilary Benn, has argued that Labour would campaign to stay in the European Union when Britain holds a referendum on the issue, expected before the end of 2017 — only to be contradicted by Mr. McDonnell, who said the party would not commit itself yet.

Mr. Corbyn will hope that his success in Parliament on Wednesday will steady the mood within Labour, though how long such civilized exchanges will last remain to be seen.

In 2005, the new leader of the Conservative Party said he was “fed up with the Punch and Judy politics of Westminster, the name-calling, backbiting, point-scoring, finger-pointing.”

That was Mr. Cameron.

A version of this article appears in print on , on Page A15 of the New York edition with the headline: Britain’s New Labour Leader Changes Parliamentary Ritual’s Tone . Order Reprints | Today’s Paper | Subscribe